With the development of ultra-large-scale integrated circuits in semiconductor manufacturing, the feature size of integrated circuits continues to decrease. In order to adapt to a reduced feature size, the channel length of metal-oxide semiconductor field-effect transistor (MOSFETs) is also continuously shortened. However, when the channel length of devices is shortened, the distance between the source and drain of devices is also shortened. Therefore, the controlling capability of gate to channel is degraded and the pinch off of channel by the gate voltage becomes more difficult, causing a subthreshold leakage phenomenon. That is, the short-channel effects (SCEs) can occur more easily.
In order to better adapt to the reduced feature size, semiconductor technologies are gradually developed from the planar MOSFET to the more efficient three-dimensional transistors, such as fin-type field effect transistor (FinFET). In a FinFET, the gate can control the ultrathin portion (fin) from both sides. Compared to the planar MOSFET, in FinFET the controlling capability of gate to channel is much stronger and the short-channel effects can be substantially suppressed. Further, the FinFET is more compatible to current integrated circuit manufacturing technologies than other devices.
However, the electrical properties of the semiconductor devices formed by current technologies are yet to be improved. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.